The present invention relates to means for rotatably mounting equipment and, while the invention could be used for mounting any type of equipment, it has particular application to the mounting of arc welding equipment. In particular, the invention is useful in robotic welding applications.
Many types of manufacturing operations are now performed robotically. In such operations, a tool or the like is automatically manipulated by a robot machine under program control. Generally, the robot machine is capable of at least three types of motion, typically rotation about three different axes. Thus, for example, the robot machine may have a body rotatable about a first axis, an articulated arm mounted on the body for rotation about a second axis and a wrist carried by the arm for rotation about a third axis, the associated tool being mounted on the wrist. Thus, the tool moves with the wrist and can undergo as many degrees of movement as are permitted by the robot machine.
However, in such prior robotic systems, the tool is moved as a unit, undergoing either translational movement or swinging or pivotal movement about some axis external to the tool. There is generally no provision for rotating a tool about its own axis. Yet such rotational movement is frequently desirable or necessary. For example, in robotic welding, a welding gun carried by the robot machine is moved along a curved welding path. There may be certain accessory equipment, such as a tracking device or a cold wire feed, in the case of Tungsten Inert Gas ("TIG") welding, which should remain in a fixed position with respect to the welding gun, and yet at the same time retain a predetermined orientation with respect to the welding path which curves in varying directions. In such applications, it would be extremely useful to be able to rotate the welding gun about its axis so that, as the welding gun is translated along the weld path by the robot machine, it can maintain the auxiliary equipment in the predetermined orientation with respect to the weld path. Existing robotic systems do not afford this capability.
One difficulty with existing systems is that the robotically mounted tool is frequently provided with associated utilities services, such as electrical wiring, fluid supplies and the like through associated conduits and, if the tool is rotated about its axis, this results in twisting of the conduits and wrapping them around associated members of the robot machine, thereby seriously impeding movement of the robot machine.